package org.test.message.common;

public final class Base64 {
    public static String encode(String code) {
        return encode(code.getBytes());
    }

    public static String encode(byte[] b) {
        int code = 0;
        StringBuilder sb = new StringBuilder((b.length - 1) / 3 << 6);
        for (int i = 0; i < b.length; i++) {
            code |= b[i] << 16 - (i % 3) * 8 & 255 << 16 - (i % 3) * 8;
            if (i % 3 == 2 || i == b.length - 1) {
                sb.append(BASE_64_CODE[(code & 0xfc0000) >>> 18]);
                sb.append(BASE_64_CODE[(code & 0x3f000) >>> 12]);
                sb.append(BASE_64_CODE[(code & 0xfc0) >>> 6]);
                sb.append(BASE_64_CODE[code & 0x3f]);
                code = 0;
            }
        }

        if (b.length % 3 > 0)
            sb.setCharAt(sb.length() - 1, '=');
        if (b.length % 3 == 1)
            sb.setCharAt(sb.length() - 2, '=');
        return sb.toString();
    }

    public static byte[] decode(String code) {
        if (code == null)
            return null;
        int len = code.length();
        if (len % 4 != 0)
            throw new IllegalArgumentException(
                    "Base64 string length must be 4*n");
        if (code.length() == 0)
            return new byte[0];
        int pad = 0;
        if (code.charAt(len - 1) == '=')
            pad++;
        if (code.charAt(len - 2) == '=')
            pad++;
        int retLen = (len / 4) * 3 - pad;
        byte[] ret = new byte[retLen];
        for (int i = 0; i < len; i += 4) {
            int j = (i / 4) * 3;
            char ch1 = code.charAt(i);
            char ch2 = code.charAt(i + 1);
            char ch3 = code.charAt(i + 2);
            char ch4 = code.charAt(i + 3);
            int tmp = BASE_64_DECODE[ch1] << 18 | BASE_64_DECODE[ch2] << 12
                    | BASE_64_DECODE[ch3] << 6 | BASE_64_DECODE[ch4];
            ret[j] = (byte) ((tmp & 0xff0000) >> 16);
            if (i < len - 4) {
                ret[j + 1] = (byte) ((tmp & 0xff00) >> 8);
                ret[j + 2] = (byte) (tmp & 0xff);
                continue;
            }
            if (j + 1 < retLen)
                ret[j + 1] = (byte) ((tmp & 0xff00) >> 8);
            if (j + 2 < retLen)
                ret[j + 2] = (byte) (tmp & 0xff);
        }

        return ret;
    }

    private static final char[] BASE_64_CODE = {'A', 'B', 'C', 'D', 'E', 'F', 'G',
            'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',
            'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g',
            'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't',
            'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6',
            '7', '8', '9', '+', '/'};

    private static final byte[] BASE_64_DECODE = {-1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            62, -1, 63, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1,
            -1, 0, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,
            14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
            -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41,
            42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1};

    private Base64() {
    }
}
